29,584 research outputs found

    Study to evaluate the effect of EVA on payload systems. Volume 1: Executive summary

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    Programmatic benefits to payloads are examined which can result from the routine use of extravehicular activity (EVA) during space missions. Design and operations costs were compared for 13 representative baseline payloads to the costs of those payloads adapted for EVA operations. The EVA-oriented concepts developed in the study were derived from these baseline concepts and maintained mission and program objectives as well as basic configurations. This permitted isolation of cost saving factors associated specifically with incorporation of EVA in a variety of payload designs and operations. The study results were extrapolated to a total of 74 payload programs. Using appropriate complexity and learning factors, net EVA savings were extrapolated to over 551MforNASAandU.S.civilpayloadsforroutineoperations.AddingDODandESROpayloadsincreasesthenetestimatedsavingsof551M for NASA and U.S. civil payloads for routine operations. Adding DOD and ESRO payloads increases the net estimated savings of 776M. Planned maintenance by EVA indicated an estimated 168Msavingsduetoeliminationofautomatedserviceequipment.Contingencyproblemsofpayloadswerealsoanalyzedtoestablishexpectedfailureratesforshuttlepayloads.ThefailureinformationresultedinanestimatedpotentialforEVAsavingsof168M savings due to elimination of automated service equipment. Contingency problems of payloads were also analyzed to establish expected failure rates for shuttle payloads. The failure information resulted in an estimated potential for EVA savings of 1.9 B

    VLA observations of 6-cm excited OH

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    The VLA was used to determine precise positions for 4765-MHz OH maser emission sources toward star-forming regions which had been observed about seven months earlier with the Effelsberg 100-meter telescope. The observations were successful for K3-50, DR21EX, W75N, and W49A. No line was detected toward S255: this line had decreased to less than 5 per cent of the flux density observed only seven months earlier. The time-variability of the observed features during the past 30 years is summarised. In addition, to compare with the Effelsberg observations, the 4750-MHz and 4660-MHz lines were observed in W49A. These lines were found to originate primarily from an extended region which is distinguished as an exceptional collection of compact continuum components as well as by being the dynamical centre of the very powerful H_2 O outflow.Comment: 11 pages, will require MN style file to process. MNRAS, accepted Oct 15, 200

    Stemming the Global Trade in Falsified and Substandard Medicines

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    Drug safety and quality is an essential assumption of clinical medicine, but there is growing concern that this assumption is not always correct. Poor manufacturing and deliberate fraud occasionally compromises the drug supply in the United States, and the problem is far more common and serious in low- and middle-income countries with weak drug regulatory systems. An Institute of Medicine consensus committee report identified the causes and possible solutions to the problem of falsified and substandard drugs around the world. The vocabulary people use to discuss the problem is itself a concern. The word counterfeit is often used innocuously to describe any drug that is not what it seems, but some NGOs and emerging manufacturing nations object to this term. These groups see hostility to generic pharmaceuticals in a discussion of counterfeit medicines. These groups see hostility to generic pharmaceuticals in a discussion of counterfeit medicines. Precisely speaking, a counterfeit drug infringes on a registered trademark, and trademark infringement in not necessarily a problem of public health consequence. Instead of talking broadly about counterfeit drugs, the WHO and other stakeholders should consider two main categories of drug quality problems. Falsified medicines misrepresent the product’s identity or source or both. Substandard drugs fail to meet the national specifications given in an accepted pharmacopeia or the manufacturer’s dossier. In practice, there is often considerable overlap between categories. There is considerable uncertainty about the size of the falsified and substandard drug market. Improved pharmacovigilance, especially in developing countries, give a better picture of the scope of the problem. In the United States, tighter regulatory controls on the wholesale market and a mandatory drug tracking system would improve drug safety. In developing countries, development finance organizations should invest in small- and medium-sized pharmaceutical manufacturers, and governments should use tools such as franchising, accreditation, low-interest loans, and task shifting to encourage private sector investment in drug retail. Finally, the WHO should work with stakeholders such as the UNODC and the WCO to develop an international code of practice on falsified and substandard drugs

    Robustness of Majorana Fermion induced Fractional Josephson Effect

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    It is shown in previous works that the coupling between two Majorana end states in superconducting quantum wires leads to fractional Josephson effect. However, in realistic experimental conditions, multiple bands of the wires are occupied and the Majorana end states are accompanied by other fermionic end states. This raises the question concerning the robustness of fractional Josephson effect in these situations. In this work, we show that the absence of the avoided energy crossing which gives rise to the fractional Josephson effect is robust, even when the Majorana fermions are coupled with arbitrary strengths to other fermions. Moreover, we calculate the temperature dependence of the fractional Josephson current and show that it is suppressed by thermal excitations to the other fermion bound states.Comment: 4+ pages, 3 figure
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